In recent years, vehicles, such as electric vehicles, fuel cell vehicles, and hybrid vehicles, configured to emit a small vehicle running sound are increasingly in practice. It is noted that, such vehicles with a small vehicle running sound are hardly recognized by a pedestrian. In consideration of this, for example, JP-A-2005-289175 discloses a vehicle proximity notification device equipped in a vehicle and configured to cause a dynamic speaker to directly radiate an audible sound as a proximity notification sound to the outside of the vehicle so as to notify existence of the vehicle to pedestrians around the vehicle. It is noted that, in order to generate a comfortable low-frequency sound using a dynamic speaker, it is required to equip a vehicle with a woofer device or the like having a large diaphragm. Mountability of such a large device becomes low, and the weight of such a large device is increased.
In such a vehicle equipped with a vehicle proximity notification device, similarly to other vehicles, two electromagnetic whistle devices (electromagnetic alarm devices) are further provided to emit a whistle sound (alarm sound) to the outside of the vehicle when a horn buzzer switch device is manipulated by an occupant. Specifically, the two electromagnetic whistle devices equipped in a vehicle configure a double-horn-type structure for emitting simultaneously whistle sound components in two different tones including first whistle sound (first alarm sound) and second whistle sound (second alarm sound) in order to generate a massive tone and to improve comfortableness of the whistle sound. In order to generate simultaneously the whistle sound in two different tones, it is necessary to equip a vehicle with both the first electromagnetic whistle device for causing the first whistle sound and the second electromagnetic whistle device for causing the second whistle sound, which is in a different tone from that of the first whistle sound.
The two electromagnetic whistle devices are configured to generate whistle sound components when receiving a direct current signal at a self-excited voltage greater than or equal to a threshold such as 8 volt. Specifically, such an electromagnetic whistle device includes:                a coil configured to cause a magnetism on receiving electricity supply;        a current interrupter configured to intermit an electricity supply circuit of the coil when a direct current at a self-excited voltage greater than a threshold is applied to the coil;        a moving iron core configured to be driven by the magnetism of the coil; and        a vibrating plate (diaphragm) joined with the moving iron core.        
For example, JP-A-58-162994 discloses an electromagnetic whistle device including a coil configured to cause oscillation of a diaphragm together with a moving iron core when a self-excited voltage is applied to the coil to cause a current interrupter to intermit electricity supply to the coil thereby to cause a whistle sound.
According to the prior arts as described above, it is required to provide two electromagnetic whistle devices in a vehicle in order to generate simultaneously a whistle sound in two different tones.